Multilayer metallization structures are becoming commonplace in the electronics industry. In such systems, a first metal layer is deposited on a suitable substrate and defined. A layer of insulating dielectric material is deposited thereover and vias are formed therein to expose a portion of the first-level metal, or the substrate. The second metal layer is deposited thereover and defined to form the remaining portion of the interconnection system. The use of borophosphosilicate glass as the dielectric material in such a structure is disclosed by Schnable and Kern in copending application Ser. No. 641,410, filed Aug. 16, 1984.
Borophosphosilicate glass (BPSG) layers and their use in the semiconductor arts are disclosed by Kern in U.S. Pat. No. 3,481,781, issued Dec. 2, 1969. The use of BPSG to form tapered openings in glass coatings in semiconductor devices is disclosed by Flatley et al. in U.S. Pat. No. 4,349,584, issued Sept. 14, 1982 and Hsu et al. in U.S. Pat. No. 4,363,830, issued Dec. 14, 1982. Such applications take advantage of the superior reflow characteristics of BPSG. In such applications, a BPSG layer is deposited over a structure and heated to fusion taper it for better coverage of topography. Vias are opened in the BPSG layer and one or more underlying layers. The structure is then heated to a temperature at which the BPSG will soften and reflow at the edges of the vias, thus producing excellently tapered vias.
BPSG layers are conventionally deposited by chemical vapor deposition (CVD). In accordance with this invention, improvements in this technique have been found which significantly improve both the deposition rate of the BPSG layer and its quality.